Its lead product Photopheresis is approved by the FDA for palliative treatment of the skin manifestations of cutaneous T-cell lymphoma (CTCL) - a form of blood cancer - in patients who have not been responsive to other forms of treatment.

Outside the US, Therakos Photopheresis is also used by doctors for immune-modulating applications in a variety of conditions including CTCL, Graft Versus Host Disease, Crohn's disease, solid organ transplants and other diseases.

This is Mallinckrodt's second major acquisition this year designed to bolster its presence in hospitals. The firm focuses on generic and specialty drugs, as well as medical imaging agents.

Mallinckrodt itself was spun off from Covidien in 2013 and has used acquisitions as a way of further its growth.